Micro RNA s in metabolism

Micro RNA s (mi RNA s) have within the past decade emerged as key regulators of metabolic homoeostasis. Major tissues in intermediary metabolism important during development of the metabolic syndrome, such as β ‐cells, liver, skeletal and heart muscle as well as adipose tissue, have all been shown to be affected by mi RNA s. In the pancreatic β ‐cell, a number of mi RNA s are important in maintaining the balance between differentiation and proliferation (miR‐200 and miR‐29 families) and insulin exocytosis in the differentiated state is controlled by miR‐7, miR‐375 and miR‐335. MiR‐33a and MiR‐33b play crucial roles in cholesterol and lipid metabolism, whereas miR‐103 and miR‐107 regulates hepatic insulin sensitivity. In muscle tissue, a defined number of mi RNA s (miR‐1, miR‐133, miR‐206) control myofibre type switch and induce myogenic differentiation programmes. Similarly, in adipose tissue, a defined number of mi RNA s control white to brown adipocyte conversion or differentiation (miR‐365, miR‐133, miR‐455). The discovery of circulating mi RNA s in exosomes emphasizes their importance as both endocrine signalling molecules and potentially disease markers. Their dysregulation in metabolic diseases, such as obesity, type 2 diabetes and atherosclerosis stresses their potential as therapeutic targets. This review emphasizes current ideas and controversies within mi RNA research in metabolism.